a) Technical Field of Invention
This invention relates to thermal transfer printing and, in particular, to a thermal transfer printing receiver sheet for use with an associated donor sheet.
b) Background of the Art
Currently available thermal transfer printing (TTP) techniques generally involve the generation of an image on a receiver sheet by thermal transfer of an imaging medium from an associated donor sheet. The donor sheet typically comprises a supporting substrate of paper, synthetic paper or a polymeric film material coated with a transfer layer comprising a sublimable dye incorporated in an ink medium usually comprising a wax and/or a polymeric resin binder. The associated receiver sheet usually comprises a supporting substrate, of a similar material, having on a surface thereof a dye-receptive, polymeric receiving layer. When an assembly, comprising a donor and a receiver sheet positioned with the respective transfer and receiving layers in contact, is selectively heated in a patterned area derived, for example--from an information signal, such as a television signal, dye is transferred from the donor sheet to the dye-receptive layer of the receiver sheet to form therein a monochrome image of the specified pattern. By repeating the process with different monochrome dyes, usually cyan, magenta and yellow, a full coloured image is produced on the receiver sheet. Image production, therefore, depends on dye diffusion by thermal transfer.
To facilitate separation of the imaged sheet from the heated assembly, at least one of the transfer layer and receiving layer may be associated with a release medium, such as a silicone oil.
Although the intense, localised heating required to effect development of a sharp image may be applied by various techniques, including laser beam imaging, a convenient and widely employed technique of thermal printing involves a thermal print-head, for example, of the dot matrix variety in which each dot is represented by an independent heating element (electronically controlled, if desired).
Receiver sheets for receipt of an image are conveniently stacked in a storage magazine adjacent to the print-head. In practice, problems are encountered in separating individual receiver sheets from the stack for smooth, sequential feeding to the print-head.
c) The Prior Art
Various receiver sheets have been proposed for use in TTP processes. For example, EP-A-0194106 discloses a heat transferable sheet having a substrate and an image-receiving layer thereon, with an intermediate layer between the substrate and receiving layer. A lubricating layer may be provided on the surface of the substrate remote from the receiving layer, and suitably comprises a synthetic resin, such as a methacrylate resin or a vinyl resin.
Even so, the problem of jamming with commercially available receiver sheets is frequently encountered during TTP operations, particularly when the operation requires the continuous sequential feeding of a large number of sheets from a single storage magazine.
We have now devised a receiver sheet for use in a TTP process which overcomes or substantially eliminates the aforementioned problem.